PHOTODECOMPOSITION AND REGENERATION OF PBI2 NANOMETER-SIZED PARTICLES, EMBEDDED IN POROUS SILICA FILMS

The photoluminescence (PL) spectrum of nanometer-sized particles of Pb I2, at 77 K, is dominated by an acceptor-like exciton emission. When t he specimens were irradiated with visible light at temperature of 70 d egrees C, the exciton energy was blue-shifted and its intensity decrea sed. This blue shift is a manifestation of a quantum size effect, and it indicates the reduction of the particle's size. The changes in the PL spectra showed strong dependence on the radiation conditions. These results suggest that the irradiation produces chemical decomposition of Pb-I bonds. Moreover, retreatment of the particles with iodine vapo rs nearly regenerated the original PbI2 particle's size.